1. Field of the Invention
The present invention relates to a fluid sealed antivibration device for use in an automobile engine mount or the like.
2. Description of the Prior Art
Such a fluid sealed engine mount is known and disclosed for example in Japanese Unexamined Patent Publication No. HEI 10-281214 (1998) in which an idle orifice passage is provided between a main fluid chamber and a sub-fluid chamber, and part of a diaphragm forming the sub-fluid chamber serves as a seating section which is adapted to open and close the idle orifice passage. In the normal condition, a pushing member is pushed to cause the seating section to close an opening of the idle orifice passage. In the idling condition, the pushing member is caused to open the seating section, wherein the seating section opens the opening of the idle orifice passage to open the idle orifice passage.
However, in the case where an opening and closing means for the orifice passage is provided, this opening and closing means may generate an abnormal sound. For example, in the case of the idle orifice passage, when large vibration at the time of starting or stopping an engine is input in the closing condition, an elastic body section elastically deforms to make the inside of the main fluid chamber positive pressure or negative pressure. As a result, sudden change of internal pressure is caused to generate a cavitation phenomenon whereby many bubbles of air are generated in the fluid. Once this phenomenon generates, the opening and closing means for closing the orifice passage may be pushed back toward the sub-fluid chamber side or on the contrary, the opening and closing means is strongly attracted to the main fluid chamber side. Thus, the abnormal sound is generated by repeating the above.